Biomaterials are sometimes used in medical applications. For example, bone grafting is a surgical procedure for repairing bones and typically involves introducing a bone graft material (which is a type of biomaterial) into an area of bone that requires repair, such as a fracture. The bone graft material is intended to stimulate growth of healthy native bone tissue, and new native bone tissue may eventually replace the bone graft material completely. Bone graft material typically includes a combination of crushed bone and a liquid component, such as blood, plasma, or growth factors. Bone graft materials can be allograft (derived from a human other than the one receiving the graft), autograft (derived from the human receiving the graft), and synthetic (created from, for example, ceramics like calcium phosphates).
Bone graft materials are typically delivered to a surgical site using syringe-like delivery devices, which often include small-diameter dispensing tips, such as cannulus devices. In addition, the components of the bone graft material are sometimes brought together and combined to form the bone graft material in the delivery device. The bone graft material is then dispensed from the delivery device. This often involves using a syringe plunger to advance an amount of bone graft material from a syringe barrel and through a dispensing tip, and then dispensing the bone graft material from the dispensing tip at the surgical site. The dispensing tip may be integrally formed with or removable from the syringe barrel, and may have various lengths.
Once the syringe plunger is completely depressed in the syringe barrel, all or nearly all of the bone graft material is expelled from the syringe barrel. However, the dispensing tip still contains an amount of bone graft material, and further operation of the syringe plunger is ineffective for advancing that bone graft material out of the dispensing tip. This prevents the bone graft material that is trapped in the dispensing tip from being used during the surgical procedure, and leads to wasting an amount of the bone graft material. Wasting bone graft material is undesirable, however, as its components are costly. In addition, this drawback to current devices requires that more bone graft material be prepared than is actually required at the surgical site, in order to offset the amount that is trapped in the dispensing tip.